Generally, a composite tube is produced by a method in which prepreg material is wound in a superposed manner around a metallic mandrel, then pressure is applied with a compacting system on this composite structure, then the thermoset and/or thermoplastic resin matrix is consolidated, and then the mandrel is removed from the product. Prepreg material is widely used in the manufacture of composite parts and structures. Prepreg material is a combination of thermoset and/or thermoplastic resin matrix and fiber reinforcement. The fibers of prepreg material are continuous fibers that extend parallel to each other. Preform is created by stacking individual layers of unidirectional tape optionally with different types of fiber, different resin matrix and/or different ply weight so that the layers of the preform contain fibers extending in different directions.
To improve the performance of the composite tube when submitted to loading specific to its use, the major portion of the reinforcing fibers of the preform should be oriented in order to improve the performance of the tube. However, existing manufacturing methods do not permit to achieve such a result at a high level of quality and without badly impacting on the homogeneity of the tube. In particular, such composite tubes are generally made by a roll wrapping process. Roll wrapping consists of wrapping preforms or individual layers of prepreg material having the same length as the tube and a width corresponding to a certain number of revolutions around the mandrel. Thus, the beginning and end of each wrapped preform or layer results in a defect in the tube. Furthermore, this roll wrapping process may require several steps to achieve the total required thickness and the quality of the tube depends on the skill and experience of the operator.
It is known to manufacture sports articles such as golf club shafts, fishing rods, rackets, etc. from a fiber-reinforced resin matrix composite material, in particular a carbon fiber composite material. However, elongate tubular shafts of carbon fiber composite material tend to suffer from the problem of exhibiting non-uniform properties, in particular a non-uniform wall thickness which leads to undesired variations in flexural stiffness along the shaft and when the flexural force is applied in different rotational orientations around the axis of the shaft.
The aim of the present invention is therefore to at least partially to overcome this problem with known shafts and to provide an improved sports article comprising an elongate tubular shaft comprised of a fiber-reinforced resin matrix composite material and manufacturing method, in particular in which the elongate tubular shaft can exhibit constant flexural properties by providing tubular shaft which has a highly concentric wall structure, with a uniformly controlled wall thickness around the axis of the shaft and accurate control of fiber alignment around the axis of the shaft.